If you think you have problems, consider the plight of the California waterfowler.

A capsule history reveals the past half-century has wrought two significant changes. First, the great northern flights of mallards that once wintered in the state were short-stopped in Washington and Oregon along the Columbia River, a result of post-World War II agriculture development that followed the construction of hydroelectric dams. This was not too troublesome to California hunters, because many dismissed mallards as trash ducks. The preferred bird was the pintail, which still winged southward in great number. Then the pintail population crashed. The sprig limit eventually was reduced to one daily and the season length restricted. This caused a change in attitude. Hunters began seeking mallards, the only big duck that could be killed in significant number.

With many northern mallards hanging out along the Columbia River, the shooting focused primarily on homegrown mallards. Fortunately, the state at first possessed a bountiful breeding population. Today, the state’s native mallards are in trouble. The population has declined to a record low, and there is a heated debate over how to arrest the decline and rebuild the state’s breeding flocks to preserve the shooting of “big ducks.”

A general analysis of California mallard data reveals the problem. We begin with an overview, looking first at California’s mallard breeding population from 1996 to present.

As you can see by the trend line, California’s breeding mallards have steadily declined, falling from 537,000 in 1996 to a record low of 262,000 in 2004. This represents a 51 percent decline.

The California mallard harvest data reflects a similar downward trend.

The trend line reveals a decreasing kill, dropping from 373,000 in 1996 to 288,000 in 2003, a decline of 23 percent.

Importantly, the breeding population declined at a faster rate than the kill, as shown in the following graph. (The green trend line represents the breeding population, the red trend line represents the kill.)

As you can see, if the present trends continue, California’s annual mallard kill will soon exceed its breeding population. If you believe the kill matters, this is cause for alarm.

This is the problem facing the state’s duck hunters and waterfowl administrators.

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Population biology’s fundamental law states that if births exceed deaths, the population will increase. If deaths exceed births, the population will decline. We therefore will first examine births and then the sport kill in an attempt to determine the causes for California’s breeding population decline.

The following graph charts California hen mallard age-ratios -- the number of juveniles per adult in hunters’ bags, the standard measure of breeding success.

As you can see by the trend line, juvenile productivity has remained virtually constant over the years in question.

But this long-term trend is misleading, as you can see in the following graph when we compare the average hen age-ratios for the years 1996-98 to 1999-02, the latter being years of widespread spinning-wing decoy usage.

The data reveals the age-ratio averaged 3.2 juveniles per adult from 1996-98, compared to 2.7 juveniles per adult from 1999-02. This represents a juvenile productivity decline of 16 percent.

At the same time, the average annual mallard harvest (both sexes) for the years 1996-98 and 1999-2003 reveals a drop in the kill.

This tells us the average mallard kill declined 26 percent, dropping from an average of 378,000 in 1996-98 to 281,000 in 1999-2003.

This decline can be misleading, because hens are key to maintaining the breeding population. We therefore must compare the average percentage of hens in the mallard bag during the same time periods.

This tells us hens averaged 34 percent of the mallard kill during the years 1996-98. This average fell to 31 percent from 1999-03. This represents a decline of nine percent, which was insufficient to offset the 16 percent loss in juvenile productivity, all other things being equal.

And this is only part of the problem.

Biologists believe adult hens are the most successful breeders, and therefore are the single most important component of the breeding population. Their preservation is key to maintaining a large breeding population and bountiful fall flights. But an examination of California hen harvest data raises alarms.

The data reveals that since the widespread use of spinning-wing decoys in 1999, the percentage of adult hens in the female bag has increased.

The data tells us adult hens averaged 24 per cent of the female kill from 1996-98 and 27 percent of the kill from 1999-02, an increase of 12 percent. This suggests the percentage of adults in the hen breeding population is declining – a factor that would significantly reduce juvenile productivity.

Interestingly, California’s sharpest population decline has occurred simultaneously with the advent of spinning-wing decoys. The following graph focuses strictly on the years 1999-2004, the year 1999 marking the first season of widespread use of spinning-wing decoys.

As you can see, the California mallard breeding population fell from 560,100 in 1999, the first season of widespread SWD usage, to 262,400, a decline of 53 percent. The lone up-tick in the population occurred in 2003 following restrictive regulations imposed for the 2002-03 hunting season.

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It is important to note these analyses do not constitute a scientific proof. But in the absence of a predictive mallard population model, which biology to date has failed to develop, we are left to draw our conclusions by examining the best commonly available data. Each data set represents a key insight, although the relationship between the introduction of spinning-wing decoys and the population decline might best be described as circumstantial. Other factors that could influence the results include changes in annual hunting regulations, wetland conditions during the breeding seasons, weather patterns during the hunting seasons, and changes in the way harvest data is tallied since 2001.

Nevertheless, the failure to significantly reduce the percentage of hens in the bag, the increased percentage of adult hens in the bag, and the decline in juvenile productivity strongly point to shooting as significantly contributing to California’s declining mallard breeding flocks and reduced autumn population. Moreover, this population decline has occurred simultaneously with the advent of spinning-wing decoys. Habitat is not a problem (See The Wrong Diagnosis , Oct. 13, 2004.)

This year’s regulations tacitly recognize the role of hunting in the population decline. Authorities reduced the season length from 99 days in 2003 to 93 days in 2004, and cut the mallard bag limit from seven to five, with no more than one hen in the bag (compared to two hens last season). But key observers do not expect these tepid restrictions to allow the population to rebuild. They believe the population will decline further next spring.

Thus, the biological data suggests that every concerned waterfowl hunter asnd administrator consider the fruits of a ban on spinning-wing decoys, along with the adoption of a more conservative harvest strategy, to prevent a further decline and allow the state’s beleaguered mallard stocks to rebuild.

*Denotes harvest estimates calculated under the Harvest Information Program, compared to the prior “post office” survey.